1. Field of the Invention
The invention relates generally to the field of display systems and more specifically to those systems including gas discharge display panels.
2. Description of the Prior Art
Display systems in which gas discharge display panels provide a directly-readable luminous output are known in the art. Such systems generally include one or more of the aforementioned display panels, a circuit for controlling the panel, and a DC power supply.
A typical gas discharge display panel has one or more anodes, a plurality of cathodes associated with each anode, the combination forming a pattern, and an envelope enclosing the anodes and cathodes. An atmosphere of a low pressure gas such as mercury is also provided inside the envelope. The gas is caused to glow when a sufficiently high voltage is established between selected anodes and cathodes that a discharge occurs therebetween. The control circuit serves to energize selected anodes and cathodes which cooperate with the gas to form a glow pattern.
The DC power supply is provided to supply the necessary voltage to the selected anodes and cathodes and may also power the selection circuitry. A typical arrangement is shown, for example, in U.S. Pat. No. 3,794,881, issued to D. Janssen on Feb. 26, 1974, which discloses a circuit for providing a stable d-c voltage to the display and selecting circuit. Sometimes, for example in an electric time clock, it would be desirable to use the 60-cycle line frequency as a frequency standard, which is not immediately available with a DC power supply. A direct connection to the AC line, however, would subject the panel and the selection circuitry to fluctuations commonly encountered in the AC line.